Induction stirrer



DEC. 2, 1952 E, LADELL 2,620,366

INDUCTION STIRRER Filed Deo. 8, 1950 2 SHEETS-SHEET 1 21. 22 24 2.52 26 30 fm1] ,/,Qde,

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Patented Dec. 2, 1952 INDUCTION STIRRER Emil Ladell, Vasteras, Sweden, assigner to Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a Swedish corporation Application December 8, 1950, Serial No. 199,740

3 Claims.

In copending application Ser. No. 172,434, filed July 7, 1950, having the same assignee as the instant application, an arrangement is described intended to induce low frequency currents in the charge of the furnace for stirring the molten charge. The arrangement consists of a multiphase winding arranged below the bottom` of the furnace and traversed by a low frequency alternating current. According to said application, the winding is arranged in U-shaped troughs of iron which are welded to or in some other Way attached to an iron core arranged below the bottom of the furnace and built up from comparatively thick iron sheets. In order to enable a good cooling of the winding, this core is divided into a plurality of parts, in order to allow cooling air to flow up between them, and further the said troughs are attached to the core only in certain points, which on one hand facilitates the cooling and on the other hand makes f the manufacturing simpler and cheaper.

The present invention concerns a modification of the arrangement described in said application and is chiefly characterised thereby that the conductors of the winding are formed by pipes traversed by a cooling liquid, preferably water, and thereby that between the winding and the bottom of the furnace a heat insulating layer of some refractory material is arranged to prevent molten metal from coming in contact with the winding in the case that the bottom of the furnace should be penetrated by the metal. This layer is further so designed, that metal which may come from the furnace, rapidly can escape aside.

In spite of the fact that good results may be obtained with the device described in the said application, it is, however, combined with the risk that the winding is damaged if the bottom of the furnace is penetrated. By the present invention any damage of the winding in such cases is avoided, because it is protected by an insulating layer, at the same time as an improved cooling can be attained thereby that the winding is cooled by a streaming liquid. In fact, the use of a liquid as cooling medium is made possible by the combination with said insulating layer, because any risk for explosions, due to contact between the molten metal and the cooling liquid, is removed by the application of said insulating layer.

The invention is most readily understood by reference to the accompanying drawing, where Fig. 1 shows a vertical section through a part of the furnace along the line B-B, in Fig. 2,

which shows a part of the furnace seen from above. Fig. 3 is a cross section through the furnace along the line C-C, and Fig. 4 a section through the winding along the line E-E in Fig. 6, which shows a detail of the section C-C in an enlarged scale. Fig. 5 shows a section along the line F-F in Fig. 6.

In the figures, l designates the lining of the furnace and 2 the molten charge, and 3 is the metallic bottom of the furnace below the lining, which bottom is made of a non-magnetic metal. 4 designates the coils of the stirring winding and 2l a cap of metal protecting the ends of the coils, and 6 a terminal block with links for connecting together the different coils. 20 designates a continuous layer of a heat resisting insulating material arranged between the coils 4 and the bottom 3 of the furnace, which layer in the case that the lining 2 of the furnace should break and the molten metal penetrate the bottom 3, prevents the molten metal from coming in contact with the coils 4.

As will be seen from Figs. 4 and 5, the coils consist of pipe-shaped copper conductors 1, which are surrounded by a comparatively thin insulation and located in U-shaped troughs of iron 8, which are divided into a plurality of comparatively short parts and extend perpendicularly to the iron cores Il, I2, and i3 (Fig. 3), which cores are piled up by thick sheets 9, l0 and l0. The sheets I0 and l0' project above the sheets 9, so that the troughs 8 will be in contact only with the rst mentioned sheets. The copper conductors 1 are held down in the troughs 8 by means of fiat bars I4 which, in their turn, are held down by bolts Il with nuts I3. These bolts are insulated from the bars 8 by means of mica washers I9. Above the bars I4, there is a continuous layer 20 of heat resisting material, i. e. some refractory material, which in the present case, when the bottom of the furnace is curved in two directions perpendicular to each other, only is curved in a plane parallel to the line B-JB but straight in a plane perpendicular to that plane. The layer 20 will, in other words, form a cylindrical surface. By this design of the layer, molten metal coming out from the bottom of the furnace easily escapes aside. The escape is still more facilitated if the insulating layer 20 is inclined a small degree. In order to protect the winding coils, they are surrounded by a cap 2l of iron sheet, which is carried by the bars I4, and the sheets l0', which are attached to the bottom of the cap 2i. The cooling liquid is delivered to and drawn off from the Winding coils by distributing boxes 22 and 23, which may be pipe-shaped and provided with a plurality of valves 24 and 25 which, in their turn, by means of rubber pipes 28 and 29 are connected to valves 28 and 27 which, in their turn, by metal pipes 30 and 3l are connected to the conductors 1 of the different coils.

In the case that one of the coils should be damaged, it can be put out of function by means of links on the terminal block 6, and the delivery of water to the said coil can also be shut off by means of valves 24, 25, 28, 21. It is thus possible to have the furnace in service also if one or a plurality of the coils should be damaged, however with a reduced stirring action.

I claim as my invention:

1. An electric melting furnace having means for the generation of a stirring magnetic eld in the molten charge, comprising iron cores located below the bottom of the furnace, channels at the upper side ofr the corea multi-phase winding having rtubular conductorsk arranged in said channels,- means for passing a cooling liquid through said conductors, said winding being traversed by a low frequency alternating current, and-a layer of heat insulating material interposed between said winding and the bottom of the furnace to intercept molten metal that may penetrate the bottom of the furnace, said layerv being spaced from thebottompf `the furnace and having` at least one side edge part thereof disposed at the lowest portion of` said layer to spill outwardly therefrom, by gravity, any molten metal received from the furnace.

2. An electric furnacev according to claim 1 in which thefurnace bottom is. curved, and the said heat insulating layer is bent to form apart of a cylinder conforming to the curvature ofthe furnace bottom.

3. An electric melting furnace having means for the generation of a stirring magnetic field in the molten charge, comprising iron cores located below the bottom of the furnace, iron troughs attached to the upper edge of said iron cores, said troughs and cores being arranged substantially perpendicularly to each other and said troughs being divided into a plurality of parts attached in alignment with each other, a multi-phase winding having tubular conductors arranged in said troughs, means for passing a cooling liquid through said conductors, said winding being traversed by a low frequency alternating current, andalayer of heat insulating material interposed between said=winding and the bottom of the furnace, said'layer being spaced from the bottom of the furnace and having at least one side edge part thereof disposed at the lowest portion of said layer to spill outwardly therefrom any molten metal received from the furnace.

EMILY LADELL.

REFERENCES CITED Thefollowing references are of' record in the le of this patent:

UNITED STATES PATENTS Number Name. DateY 428,379 Colby May A20, 1890 1,818,107 Taylor Aug. 11, 1931 1,834,445 Brace Dec. 1, 1931 1,861,870 Long June 7, 1932 1,922,034 Feehan Aug, 15, 1933 2,041,333 Gruber et al May 19, 1936 2,363,582 Gerbereta-l. Nov. 28, 1944 2,433,495 Vogel Dec.,30, 1947 2,513,082 Dreyfus- June 27, 1950 

